feat(i18n): localize start/help/menu, practice, words, import, reminder, vocabulary, tasks/stats for RU/EN/JA; add JSON-based i18n helper\n\nfeat(lang): support learning/translation languages across AI flows; hide translations with buttons; store examples per lang\n\nfeat(vocab): add source_lang and translation_lang to Vocabulary, unique constraint (user_id, source_lang, word_original); filter /vocabulary by user.learning_language\n\nchore(migrations): add Alembic setup + migration to add vocab lang columns; env.py reads app settings and supports asyncpg URLs\n\nfix(words/import): pass learning_lang + translation_lang everywhere; fix menu themes generation\n\nfeat(settings): add learning language selector; update main menu on language change

migrations/versions/20251204_add_vocab_lang_fields.py

@@ -0,0 +1,30 @@
+"""add source_lang and translation_lang to vocabulary
+
+Revision ID: 20251204_add_vocab_lang
+Revises: 
+Create Date: 2025-12-04
+"""
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '20251204_add_vocab_lang'
+down_revision = None
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.add_column('vocabulary', sa.Column('source_lang', sa.String(length=5), nullable=True))
+    op.add_column('vocabulary', sa.Column('translation_lang', sa.String(length=5), nullable=True))
+    # Create unique constraint for (user_id, source_lang, word_original)
+    op.create_unique_constraint('uq_vocab_user_lang_word', 'vocabulary', ['user_id', 'source_lang', 'word_original'])
+
+
+def downgrade():
+    op.drop_constraint('uq_vocab_user_lang_word', 'vocabulary', type_='unique')
+    op.drop_column('vocabulary', 'translation_lang')
+    op.drop_column('vocabulary', 'source_lang')
+